We do not pre-bake as an internal rule and never a complaint. Obvious
exceptions: We are washing or cleanliness testing the boards. Then we will
bake them dry before masking and coating. Or the customer specifically
requires a pre-bake on the drawing. (I always then ask the question; "How
long after the bake do I have to coat them before they need to be baked
again?" Strangely, only a few have an answer for that.)

I have visited many facilities that conformal coat and I have witnessed it
both ways but mostly on the "no pre-bake" side. One customer even pre-baked
their boards before coating with a water based acrylic.

Lloyd Duso
Plant Manager
Diamond-MT
(814) 535-3505
www.Diamond-mt.com

On Tue, Feb 28, 2017 at 2:39 PM, Douglas Pauls <
[log in to unmask]> wrote:

> Lee,
> It Depends.
>
> We have one facility that has never baked prior to coating application.  No
> evidence of any conformal coating related problems.  We have several
> facilities that bake religiously prior to coating application, also for
> acrylic.  No evidence of any conformal coating related problems.
>
> I think the biggest factor is how much residual water you have.  I don't
> think your assemblies have to be bone dry before coating.  We do a lot with
> in-line aqueous cleaners, which have heated air knifes that remove the bulk
> of the water.  Now, there might still be some entrapment areas, but if so,
> we find them and then blow out those entrapment areas with ionized air.
>
>
> Doug Pauls
> Principal Materials and Process Engineer
> Rockwell Collins
>
> On Tue, Feb 28, 2017 at 10:20 AM, Lee Hitchens <
> [log in to unmask]
> > wrote:
>
> > Hi all
> >
> > I've recently been asked about baking pcbs before conformal coating and
> > whether there is any quantified data on the effect on coating
> performance.
> >
> > Does anyone know of any public studies on this or can shed some light on
> > its effectiveness beyond anecdotal experience ? I would be very grateful
> to
> > you on this.
> >
> > Best Regards
> >
> > Dr Lee Hitchens
> >
> > SCH Technologies is a Division of SCH Services Limited
> >
> > www.conformalcoating.co.uk
> > Skype: leehitchens
> >
>